The present invention relates to a shield cap for a shield-type mining support or a shield support for underground mining. The shield cap or shield support includes a cap plate, with reception devices for the connection of hydraulic cylinder heads to the shield cap, and a supporting structure welded below the cap plate and having a plurality of longitudinal spars.
Shield supports, the height of which is variable by means of hydraulic cylinders, have been used for decades in underground mining and, as a rule, have two floor runners, a link mechanism, an impact shield and a one-part or multipart shield cap connected to the impact shield in an articulated manner. By the mostly two, sometimes even four hydraulic cylinders being extended, the shield cap is pressed against what is known as the hanging roof, that is to say the top rock, of an underground longwall face, in order to keep free in the underground rock a chamber, mostly designated as a longwall face, for arranging the mining machines. A plurality of shield supports or shield support frameworks of adjustable height form a self-advancing support which, by the hydraulic cylinders being retracted and by individual shield supports being moved along, can be drawn forward via approximately horizontally oriented advancing cylinders braced against the mining plant, or via which a mining plant can be pushed forward.
The shield support frameworks or shield supports used in high-performance mining operations comprise shield caps, the cap plates of which have lengths of five meters and more and widths of two meters and more. By means of the supporting structure welded below the cap plate, in this case all the bending forces between the cap tip and the cap end or the reception devices for the ram heads have to be absorbed with high reliability, in order to avoid a fracture of the shield cap given the case of loose or undulating rock against which the shield cap is pressed. In order to withstand these loads, the shield support frameworks used at the present time mostly have a supporting structure produced in a box type of a construction and having a multiplicity of longitudinal spars which consist of sheet metal strips and which are stiffened via transverse plates. In a shield support with a draw-off orifice, such as is described, for example, in DE 198 14 246 A1, two box profile-shaped longitudinal spars are provided which extend over the entire length of the shield cap and at the same time form the guide device for a sliding plate in order to provide the openable and closable draw-off orifice in the shield cap for the draw-off extracting method.